New Hampshire Republicans have a track record of picking presidential candidates who often go on to win their party's nomination. Usually, that means bolstering establishment candidates. But this year, billionaire Donald Trump is polling far ahead of the rest of the pack. That leaves his rivals fighting amongst themselves in the hope that one of them can take down Trump in the state that holds the first primary.

There's not much time left for establishment Republicans to settle on a favorite. And with no clear challenger to Trump's dominance in New Hampshire, other candidates and their superPACs are lobbing attack ads at each other.

One ad from New Jersey Gov. Chris Christie opens with the words, "Marco Rubio is attacking Gov. Chris Christie." It's a response to the Florida senator's criticism of Christie's record on a range of issues, including gun control.

That back and forth continued on the campaign trail in New Hampshire on Friday. During a stop at a weapons factory in Newport, Rubio was presented with a hunting rifle before addressing a room full of plant workers.

"I'm gonna tell you what's really important, that our nominee be someone who is a strong supporter of the Second Amendment. And there are Republicans running who are not supporters of the Second Amendment, in the way you and I want them to be," Rubio said.

In addition to attacking Christie's record on gun control, which evolved over time, Rubio has made an issue of Christie's close working relationship with President Obama after Hurricane Sandy battered New Jersey. It's all meant to question Christie's conservative credentials.

A few hours later in Hollis, N.H., Rubio himself was the target of attacks from former Florida Gov. Jeb Bush.

"The senators sometimes get off into their world, their little ecosystem of Washington, D.C.-talk. I don't know if you've noticed. It's mind-numbing, actually," Bush said.

Bush joked that Rubio, and Sen. Ted Cruz of Texas, live in an "alternative universe." He also took aim at Trump, after a member of the audience asked how Bush could distinguish himself in a year when voters seem to favor big personalities. Bush said he plans to stay the course, arguing that having the ideas and experience to be president should be enough.

"And if it isn't, I'm not gonna change who I am. I'm just not gonna do it. I'm not gonna play the game. I'm not gonna insult someone just because I'm told that's the way to connect with voters," Bush said. "Really? Really? I mean Trump does this, and it sets me off."

Afterward as the crowd thinned, Milt Janosky and Jim Polus, both of Hollis, stayed to chat about the race. Janosky said he likes Bush, but he's also considering Christie, Ohio Gov. John Kasich, and former Hewlett Packard CEO Carly Fiorina.

Janosky said he's definitely not voting for Trump, calling him "dangerous."

Polus is supporting Bush, but said there are a lot of good establishment choices.

"People like myself and Milt – we have three or four candidates that we think could be good. So that vote is being split four different ways," he said.

Janosky said those voters could easily defeat Trump — if they could just settle on one candidate they could all support.